The Great Barrier Reef abounds with life. But it is under attack from above and below the water. A team of marine biologists and geologists investigate the clues of how the reef was born, what makes it thrive and how it may disappear within our lifetime. Biologists take us below the water to discover the foundations of the reef, the submerged fresh water rivers that feed it and cycle of life that keeps it alive. But modern influences now threaten the Great Barrier Reef, and many believe it won't last another century. Watch this episode and find out.